Peroxidases and laccases are well described as enzymes which can be used to catalyse the oxidation reaction of a substrate with hydrogen peroxide or molecular oxygen, respectively. Several applications of these enzymes in oxidative processes have been described. Such applications include, amongst others, stain bleaching and anti dye-transfer in detergents, polymerization of lignin, in-situ depolymerization of lignin in Kraft pulp, bleaching of denim dyed garments, polymerization of phenolic substances in juices and beverages and hair bleaching (WO-A-92/18683, WO-A-95/07988, WO-A-95/01426).
WO-A-91/05839 (Novo Nordisk) discloses enzymatic anti dye-transfer compositions comprising an (a) an enzyme exhibiting peroxidase activity and a source of hydrogen peroxide or (b) an enzyme exhibiting oxidase activity on phenolic compounds. The compositions are said to bleach any dissolved dye so that no dye can redeposit upon the fabric.
Characteristic to peroxidases and laccases is that they have little substrate specificity. Most small phenolic molecules are substrates to these enzymes. The range of molecules which can be oxidized by these enzymes can be extended by the addition of so-called enhancers. These molecules are then the primary substrate for the enzymes. Upon reaction with the enzyme, the enhancers are oxidized to generate radicals which subsequently oxidize the final substrate of interest.
Several classes of molecules have been described as enhancers for peroxidases and/or laccases. Among these are simple substituted phenols, benzidine derivatives, phenothiazine derivatives, and azino compounds (WO-A-94/12619, WO-A-94/12620 and WO-A-94/12621, all Novo Nordisk). The value of these enhancers has been demonstrated in anti dye transfer compositions for detergents.
Whereas enhancers broaden the range of substrates which can be oxidized by the enzyme, they do not incorporate any substrate specificity in the oxidation process. To the contrary, addition of enhancers renders the oxidation reaction more aggressive and difficult to control.
We have now surprisingly found that it is possible to control the enzymatic oxidation reaction by incorporating substrate selectivity into the enhancer molecule. The addition of a selective enhancer was found to allow the tailoring of the otherwise largely random oxidation process.
Moreover, we have identified an experimental procedure which allows the development of such selective enhancers. We have found that peptides, which selectively bind the substrate to be oxidized by a peroxidase or a laccase, can act as such an enhancer. Therefore, for the identification of selective enhancers, one needs to screen for peptides which bind to the molecule to be oxidized, and then from those binding peptides, screen and/or develop a peroxidase/laccase enhancer.
The use of peroxidases and laccases with enhancers has so far most extensively been described in the areas of pharmaceutical kits and detergent anti dye-transfer compositions. Especially in the latter application, incorporation of selectivity in the bleach reaction is of high value. For dye-transfer prevention, the dye should only be bleached in solution, without causing dye damage to the fabric. Stain bleaching compositions should be targeted towards oxidation of the stain chromophores, as opposed to the dye molecules on the garments.